1. Technical Field
The present invention relates to a multi-radio mesh network system supporting at least two different wireless communication standards and a method of controlling the same.
2. Related Art
In general, unlike conventional wired networks, wireless networks have many limits in performance due to unique characteristics of wireless data communication, such as signal interference upon data transmission/reception, etc.
In order to overcome such fundamental limits, there is ongoing research and development aimed at building a single network which would reduce signal interference and maximize throughput using various wireless access techniques.
Such research and development has been further accelerated by the development of a chip supporting multi-radio, as well as advances in wireless technology and hardware manufacturing technology.
In a wireless network, a common transceiver operates in a half-duplex mode. In other words, one transceiver cannot simultaneously perform data transmission and reception. When one node within a transmission/reception range performs transmission/reception, signal interference interrupts a counterpart's communication.
Recently, to overcome the limits of wireless communication, a multi-hop mesh network has sometimes been built.
In this respect, according to a multi-hop mesh, multi-wireless communication standards, such as Institute of Electrical and Electronics Engineers (IEEE) 802.11a/b/g, world interoperability for microwave access (WiMAX), etc., are used. Several hardware interfaces using the same wireless communication standard are installed at one node, and mutually orthogonal channels are allocated to the respective interfaces, thereby enabling simultaneous transmission/reception without signal interference and increasing the throughput of the conventional multi-hop mesh wireless network.
In addition, according to different wireless communication standards, a user access link and a mesh link are sometimes classified and used.
Using the above-mentioned method, wireless mesh networks which are currently under development maximize the throughput of a wireless multi-hop backhaul network while minimizing signal interference.
However, the Ambient Network project of wireless world research forum (WWRF) suggests one multi-radio architecture in a conventional multi-hop mesh network.
The architecture has been suggested to use optimal wireless resources when current terminals are improved so as to access several access networks using several wireless techniques. To use several wireless resources in the architecture, the following three concepts are mentioned:
1) Multi-radio Transmission Diversity (MRTD);
2) Multi-radio Multi-hop (MRMH); and
3) Multi-route Transmission Diversity (MroTD).
Multi-radio access is a fundamentally different wireless access technique or denotes wireless access using an uncoupled wireless channel in single wireless technology.
In such a multi-wireless environment, of the three types, MRTD is enabled by a wireless re-selection rate, data parallelism by simultaneous multi-radio access, and duplicate data transmission to multi-radio access for transmitting reliable data.
The fundamental architecture of the suggested MRTD necessarily requires constant, periodic monitoring of a wireless resource state to select wireless resources for MRTD.
A monitoring result is provided as feedback to an access selector, optimal wireless resources are selected on the basis of the monitoring result, and user data to be transmitted is transferred to a lower layer.
In this regard, the data transferred to a specific wireless link of the lower layer is stored in the queue of the corresponding wireless link according to a traffic load to be transmitted, and is retained on standby until it is transmitted.
Therefore, when a problem occurs for some reason at a selected wireless link, the user data to be transmitted is dropped or retained on standby until the link returns to a normal state. Thus, the suggested MRTD is excessively dependent on a used time scale in a measured report. In other words, the MRTD does not efficiently cope with variation in the state of a wireless link over time.